Instructions
Beat the fifth boss, the demon Ninetails. Ninetails lives on Oni Island in the Ryoshima Coast area.
Enter Sei-an City. Find the entrance to the city at the far north end of Ryoshima Coast.
Walk straight through the city until you reach the Aristocratic Quarter. Head to Queen Himoko's palace.
Jump up the palace stairs. Look for a ledge near the palace entrance. Follow the ledge to the back of the building. You will see a spring and four rocks.
Hold down the "B" button to pull up the brush painting screen. Point the Wii Remote at the spring and hold down "A."
Draw a line from the spring to each of the four rocks to perform the Watersprout technique. When you do this, the god Nuregami will appear and grant you the Deluge technique.